marathon. that coupled with the speed of the first responders and the medics at the various hospitals. that must have saved quite a few lives, sanjay. >> reporter: yeah, there's to question. and i'll tell you, i've talked to so many doctors now, some of these are seasoned physicians, they've been working in the job for 20 years, some of them are brand new, still in training, and you hear a common sentiment, and i've seen this myself in my practice and when i've covered these stories abroad, you do the job. go in there, they can recognize what the issue is, what the injury is, and they do the job. but after some time, they do get an opportunity, piers, to reflect on what has happened as well, and to sort of recognize the scope and magnitude of it. i talked to three residents, doctors in training, and these were doctors very much on the front line of this, these are the guys waiting when they got there.